Silver halide emulsions containing 2-amino imidazoles as fog inhibitors



United States Patent 3,511,663 SILVER HALIDE EMULSIONS CONTAINING 2- AMINO IMIDAZOLES AS FOG INHIBITORS Brunello Mariani and Luigi Basaglia, Milan, Italy, assignors to Ferrania, S.p.A., Milan, Italy No Drawing. Filed Sept. 29, 1965, Ser. No. 491,390 Int. Cl. G03c l/34 US. Cl. 96109 8 Claims ABSTRACT OF THE DISCLOSURE Silver halide photographic emulsions are shown containing a 2-amino imidazole as a fog inhibitor.

This invention relates to the stabilization of photographic silver halide emulsions by Z-arnino-benzimidazoles.

It is known that photographic emulsions coated onto a support have a tendency to lose desirable photographic characteristics upon aging. In particular, loss of sensitivity and the appearance of chemical fog is often observed. To minimize such changes various stabilizers have been added to the photosensitive emulsion. Such stabilizers include sulfinic or seleninic acids, triazoles, tetrazoles, indazoles, mercaptoazoles, diaryl-iodonium salts, potassium 'bromide, etc. Although certain benzimidazoles have been suggested for this purpose, in practice they tend to cause undesirable loss of sensitivity.

An object of this invention is to provide new photographic stabilizers and stabilized photosensitive layers.

Still another object is to provide a means for stabilizing photosensitive layers without objectionable loss of sensitivity due to the presence of stabiizers.

Other objects and advantages will become apparent from the following disclosure.

It has been found that eflicient stabilization of photosensitive silver halide emulsions and fog inhibition can be achieved without a significant loss in sensitivity by incorporating in the emulsion a Z-amino imidazole, preferably having the structure wherein D represents atoms necessary to complete an aromatic ring moiety, such as benzene or naphthalene.

3,511,663 Patented May 12, 1970 These compounds may also exist in the imine form as ,-CNH D /C=NH The aromatic moiety may be unsubstituted or substituted, for example with alkyl, aryl, aralkyl, alkoxy, halogen, nitro, sulfamide, etc. without affecting its utility as a stabilizer. Although the mechanism is not fully understood, it is believed that the ability of the compounds of this invention to exist in the form of either the imidazole or imine may be important in achieving stabilization without significant sensitivity loss.

The stabilizers of this invention are normally used in amounts from 5 to 100 milligrams per kilogram of wet photosensitive emulsion, to which they may be added in water, alcohol or acetone solution, preferably after the remelting or second digestion and prior to coating the support or film base. These stabilizers are particularly eflicient when used in gelatin emulsions of silver halide, e.g. silver chloride, silver bromide-silver iodide, silver bromidesilver chloride. Their use does not preclude the use of convention emulsion additives, including optical sensitizers, chemical sensitizers, gold, platinum, palladium, rhodium, iridium, tallium and cadmium salts, color formers, surface active agents, hardeners, etc.

The following examples are presented for purposes of illustration and not for purposes of limitation.

Variable quantities of stabilizers of the above-mentioned type were added to 1 kilogram samples of the fast type gelatin emulsion containing silver bromide and silver iodide (10% silver halides of which 96% were bromide and 4% were iodide). The emulsions were then coated onto photographic film base. All samples were sensitometrically checked after coating without aging and after coating and accelerated aging (20 days at C. and 40% relative humidity). Results are given in Table I.

In Table II the examples were prepared and tests in the same manner as the examples in Table I, the emulsion being further optically sensitized with N,N-diethyl-mesomethylthiacarboxyamine iodide.

As will "be seen in the following tables, the sensitivity does not appear to be significantly altered by the presence of the stabilizers. Similar results were obtained when the stabilizers of Table I were incorporated into an emulsion of silver chloride-silver bromide of the type used for fast enlargement papers.

TABLE I Fresh Aged Mg per kg. of Relative Relative Stabilizer emulsion Fog sensitivity Fog sensitivity Example 1 None 0. 05 100 0. 25 73 2 Q-aminobenzimidazole 5 0.04 100 0.18 3 do 25 0. 04 100 0.10 4 0. 04 100 0. 09 96 5 0. 04 0. 1O 97 25 0. 03 102 0. 09 99 100 0. 02 100 0. 08 99 5 0. 04 104 0. 09 99 25 0. 03 100 0.08 99 100 0. 03 100 0. 08 99 5 0.03 100 0.08 100 25 0.02 95 0. 06 100 100 0.02 90 0. 04 98 5 0. 04 100 0. 09 98 25 0.03 100 0.06 98 TABLE II Fresh Aged Mg per k of Relative Relative Stabilizer emulsion Fog sensitivity Fog sensitivity Example 16.. None 0.06 100 0.24 81 17 2-amino-5-methoxybenzimidazole.. 5 0.04 100 0.06 102 1R dn 25 0.03 100 0.06 98 19... do 100 0.02 99 0.04 95 Z-amino-naphthimidazole 5 0.05 100 0.09 108 21 do 0.03 100 0.05 100 22 do 100 0.02 100 0.04 96 23 2-amino-5-nitrobenzimidazole 5 0.04 95 0.06 98 24 do 25 0.02 0.06

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A photosensitive silver halide emulsion layer containing therein as a fog inhibitor a stabilizing amount of a 2-amino imidazole of the formula c&

\C-NH2 N wherein D represents atoms necessary to complete an aromatic ring moiety.

2. A photosensitive silver halide emulsion layer containing therein a stabilizing amount of Z-aminobenzimidazole as a fog inhibitor.

3. A photosensitive silver halide emulsion layer containing therein a stabilizing amount of 2-amino napthimidazole as a fog inhibitor.

4. A photosensitive silver halide emulsion layer containing therein a stabilizing amount of 2-amino-5-methoxybenzimidazole as a fog inhibitor.

5. A photosensitive silver halide emulsion layer containing therein a stabilizing amount of Z-amino-S-nitrobenzimidazole as a fog inhibitor.

6. A photosensitive silver halide emulsion layer containing therein a stabilizing amount of Z-amino-S-chlorobenzirnidazole as a fog inhibitor.

7. An aqueous silver halide emulsion containing therein from 5 to milligrams per kilogram of emulsion of a Z-amino imidazole of the formula I I D References Cited UNITED STATES PATENTS 2,324,123 7/1943 Weissberger 96-109 X 3,023,103 2/1962 Dersch et a1. 96107 X 3,255,202 6/1966 Johnson 96109 X FOREIGN PATENTS 390,037 3/ 1933 Great Britain.

NORMAN G. TORCHIN, Primary Examiner R. E. FIGHTER, Assistant Examiner 

